Device for obtaining mechanical characteristic of coins

ABSTRACT

A device and procedure for obtaining the mechanical characteristics of coins includes an element onto which coins pass which element is elastically deformable under the weight of the coins. This elastically deformable element has sensors to detect an electric signal corresponding to the deformation of the element from which can be obtained the inherent mechanical characteristics sought after in the coin. From the signals produced by the coin rolling along the aforementioned element, which can be in the form of a beam, the device uses frequency analysis to determine a parameter which is representative of the mechanical elasticity of the coin. This parameter is then compared to various stored data to determine whether or not the coin is authentic.

The invention herein described refers to a device used to ascertain themechanical characteristics of coins, for their application to coinselectors or verifiers used in coin operated machines.

Electronic selectors are known to obtain certain characteristics ofcoins, fundamentally electromagnetic and measurement characteristicsthrough electro optical, inductive and, to a lesser extent, capacitivesensors.

With these types of selectors it is possible to obtain electric signalswhich bear a relation, for example, to the diameter of the coins, to thethickness, to the electric conductivity, to the magnetic permeabilityetc. The electric signals obtained are then compared with predeterminedvalues so as to identify the coins and their ensuing acceptance orrejection.

Electronic selectors of the kind commented on have been described, forexample, in British patent 2,151,062, the U.S. Pat. No. 8,403,015, andSpanish patents 540,860, 540,229 and 555,181.

Additionally, there are selectors which detect mechanicalcharacteristics of coins, such as, volume, elasticity, etc. By analysingthe impact of the coin on a beam or by determining the weight of thecoins.

Selectors, in which the impact of the coins is analysed, have beendescribed, for example, in the Swiss patent numbers 645,201 and 647,608,in the Spanish patent 514,234 and in the British patent 2173624. Themeasurement of the impact of the coins is not precise, as the impactbrings about irregular effects which are not very repetitive, dependingon the condition of the edge of the coin, the angle of incidence, thetypes of materials of coins and the anvil or sensor plate which receivesthe impact, etc.

Selectors which measure the weight of the coins have been described inthe Swiss patent 624,500, the British patent 2010559 and the Frenchpatent 2335005.

The Swiss patent 624,500, refers to a coin verification device forautomatic vending machines based on the measurement of the weight of thecoins by means of a weighing device or electronic scale.

The British patent 2,015,559 refers to an apparatus for detecting thevalue of a coin, in combination with coin dimension detector mechanismsincludes a weight sensor made up of a mobile plate with aphototransistor incorporated which detects the position of this plate.To determine the weight of the coin it is necessary for the coin to beretained.

The French patent 2335005 refers to a coin controlling device, whichincludes a mechanical weighing device in the form of a roman scale whichchecks if the coin is of the minimum weight.

The device which is the subject of the present invention, corresponds tothe latter of the above mentioned sensors which is based on themeasurement of the weight of the coins.

The device subject of the invention weighs the coins by detecting thedeformations tolerated by an elastically deformable element, on whichthe coins fall.

In the Swiss patent 624,500 the weight of the coins is measured bydetecting the displacement of a mobile element, on which the coins fall.In the device subject of the invention there is no such mobile element,but rather a deformable elastic element. The weight sensor used isdifferent.

In comparation with the British patent 2010559, the detector subject ofthe present invention does not need to retain the coin in order tomeasure its weight. In other words, with a static measurement, thedevice subject of the invention realizes a dynamic measurement. On theother hand, the element with which the weight of the coins is effected,is of a completely different nature.

Finally, the device subject of the invention uses a weighing elementwhich is different from that of the French patent 2,335,005, which onthe other hand, only checks if the coin possesses the minimum weight,that is to say, it detects the possible lack of weight but not thecorrect weight of the coin. Nor does it provide electric signals forlater checks and comparisons.

The present invention incorporates a device for ascertaining mechanicalcharacteristics of coins, applicable to coin selectors, which enablesthe identification of coins on the basis of detecting the deformationstolerated by a deformable elastic element, preferably of a metallicsubstance on which the coin rolls, the deformations produced on thiselement will depend on the weight of the coin and on the position of thecoin at each stage in relation to the deformable element.

To measure the deformations of the deformable element any of the director indirect procedures, applicable to the measurement of deformations onmaterials, may be used.

According to a preferred form of procedure, the elastically deformableelement is composed of a beam with at least one of its ends embedded.This beam determines the route along which the coin will roll, bringingabout the deformation of the beam to an extent which will depend on theweight of the coin and on its position in relation to the point ofincasement of the beam. The beam also includes a measurer ofdeterminations.

This device will form part of a coin selector and the deformable elasticelement will define a path along which the coins will pass on their waythrough the selector.

The aforementioned may be made up of an elastic band which is embeddedat one end and has the other overhanging.

The measurer of deformations may consist of an extensometer gageattached to the metallic strip, near its incasement. This measurer mayalso consist of a displacement sensing device which measures thedeflection of the point of maximum deformation on the beam.

The strip which defines the elastically deformable element may beattached at its free end. By way of variation, the beam or elastic bandmay be embedded at both ends.

In addition to the beam which defines the elastically deformableelement, an upper stretch may be included which will define the routealong which the coins will roll, and a lower stretch which will serve asan anchorage for the body of the selector. At the very least, the firststretch mentioned will have a slight inclination so as to induce therolling of the coins.

The invention also includes a procedure for ascertaining mechanicalcharacteristics of coins by means of the device herein described.

The signal obtained from the impact and rolling of the coin on theelastically deformable element, the subject of the invention, includestwo fields which are clearly distinguishable by the different activationcaused in both (frequency fields), one of these fields corresponds tothe moment of impact of the coin on the elastically deformable elementand the other corresponds to the variable signal which is producedduring the rolling of the coin along the aforementioned element and wichdepends on the weight of the coin and its position throughout.

The procedure is based on the degree of impact of the coin on thedeformable elastic element in order to determine, by means of a specificfrequency analysis, a parameter which is representative of themechanical elasticity of the coin. For this purpose a measurement of theupper harmonics of the impact signal is made, the content of thismeasurement representing the mechanical elasticity of the coin.

The invention therefore uses frequency analysis techniques with the aimof analysing the resonance frequencies in relation to the type ofimpact. If the coin is high in elasticity, the frequencies tend to beproportionately more active than if the coin is low elasticity, in whichcase the coin acts like a shock absorber. Therefore, analysing theharmonic content of the signal produced by the impact, it is possible toobtain a measurement which is representative of the elasticity of thecoin.

To carry out a measurement of the frequency occurring on impact, aparameter depending on the mechanical elasticity of the coins is usedand stored in the coin selector memory and used later to identify thecoins, together with other parameters representative of, for example,weight, alloy, dimensions, etc.

The frequency analysis of the impact described can be carried out bymeans of a circuit which includes: an amplifier, responsible forincreasing the level of the signal supplied to the impact sensor; ananalogic pitch band filter circuit, syntonised with the normal frequencyof the sought after elasticity, an analogic-digital converter and amicroprocesor. The analogic filter may be of a fixed or variablepitch-band frequency depending on whether one or various frequencyranges are involved. Furthermore, as an alternative to the analogicfilter, it is possible to use digital filtering, incorporated in themicroprosessor used in the coin selector.

If one should wish to incorporate a measurement of characteristicvibrations present during the rolling or displacement of the coin alongthe beam, it is possible to use a circuit similar to the one previouslydescribed.

As an alternative, it is also possible to use a single analogic filter,obtaining different frequency tuning during variable tuning or lineswitching techniques (usually tuning capacitors) controlled by theprocessor.

The characteristics of the invention as they are presented in theclaims, are more easily understood from the following description, madewith reference to the attached drawings in which a possible form ofprocedure shown, offered by way of example but by no means meant to belimiting.

FIG. 1 shows a schematic drawing of a device for ascertaining mechanicalcharacteristics of coins, made up of a beam embedded at one extreme.

FIG. 2 shows a diagram of the force of the coin on the beam submitted toflexion.

FIG. 3 corresponds to a possible circuit which can provide currentswhich are proportional to the deformation of the elastically deformableelement.

FIG. 4 is a diagram of the electric signal derived from the deformationsof the elastically deformable element during the rolling of the coin.

FIG. 5 shows a perspective of a possible effect on the deformableelastic element.

FIG. 6 shows a lower plan of the element in FIG. 5.

FIG. 7 shows a frontal elevation of the internal part of a coin selectorwhich includes the deformable elastic element of FIGS. 5 and 6.

FIG. 8 offers a perspective of the performance of FIG. 7.

FIGS. 9 and 10 show a lateral elevation, of other effects of theelastically deformable element.

FIGS. 11 and 12 correspond to other graphs, which represent thefrequency content of the impact of two coins, of the same dimensions,but of different elasticity, the graph of FIG. 11 corresponds to a legaltender coin and FIG. 12 to a fake coin.

FIG. 13 is a block diagram of a circuit which allows the process to becarried out.

In FIG. 1 the deflections marked number 1, indicate the route followedby coin, for example, within the coin selector. A stretch of this routeis defined by the device which is the subject of the invention andincorporates an elastically deformable beam (2) which is incased at oneextreme (3) and overhanging at the other extreme. This beam, along whichthe coins (4) will roll, may be of a metallic plate.

As a coin (4) rolls along the embedded plate (4) a deformation isproduced. This deformation will reach a maximum value when the coin (4)arrives at the free end (5) of the plate or beam (2), at which time theplate will be in a position represented by the dotted lines andreference numbered 2a. The maximum deformation corresponds to thedeflection (6).

The deformation of line 5, will always be in relation to the weight ofthe coin (4) and to its position throughout the length of the beam (2).To measure these deformations it is possible to use extensometric gages(7) attached near the incasement of the beam, without this techniquenecessarily excluding other possible procedures or systems of measuringdeformations in the plate. Hence, for example, the measurement of thedeformations may be done by displacement capacitors (without contact) intheir multiple variations (inductive, capacitive, etc.).

When the plate or beam (2) is in a totally horizontal position, theforce produced by the coin and hence producing the flexion, will be itsown weight (F-m×g).

If the plate is at an angle with the horizontal position, as seen inFIG. 2, the force provoking the flexion will be made up of the weight ofthe coin, in the normal direction of the plate (F=m×g×cos alfa).

In order to measure the deformation produced, it will be sufficient toattach an extensometer gage on the base of the plate, near theincasement, which is the most sensitive area. The gage may be arrangedusing auxiliary resistances or other gages, on a Wheastone bridgesassembly (half or complete).

Using any of the typical signal condition circuits for Wheastonebridges, it is possible to obtain, at the circuit exit, an electriccurrent related to the deformation experienced by the incased plate, asillustrated in FIG. 3. With a methodical analysis of this electriccurrent, various mechanical characteristics of the coins could bedetermined.

For example, it could be possible to determine the volume of the coins,obtaining the principal component of the resulting electric signal. Thissignal will increase gradually until the coin goes beyond the end of theplate (2)m at which time it will return to the value indicated prior tothe passing of the coin. FIG. 4 represents the electric current obtainedas the coin passes; dO y dl corresponding to those of the beginning andend of the roll of the coin along the plate (2).

In this way it is also possible to calculate the volume of the coin bycarrying out a frequency analysis of the electric signal obtained as, inaddition to the principal component, (proportional to the weight of thecoin), it is possible to find the correct frequency for the plate-coinunit. These frequencies will vary, depending on the coins inserted.

Finally, if the coin has a polygonal edge or the circular edge is ridgedor fluted, it is possible to extract from the electric signal obtained,a component generated by the small vibrations produced by the edge ofthe coin as it rolls along the plate, therefore obtaining informationabout the shape of the coin.

Plate (2) may be supported at the free end or even encased at both ends,hence obtaining optimum flexion when the coin is halfway along theplate.

Plate (2) also allows shock absorbing material to be attached with theaim of filtering from the sensor, components of the electric signalobtained which are of a higher frequency than the basic and which are nolonger required.

If the coin (4) should fall on sheet (2), it is possible to position ashock absorbing block in front of this sheet so as to deenergise thecoin.

The beam or metallic strip will preferably be of metal, although itcould also be made from non metallic materials, such as a composite basewhich is shock absorbing.

The beam represented in FIGS. 5 and 6 constitutes the upper route,reference marked 10, which defines the coin pathway, and a lower routenumber 11, which operated as an anchorage area for the beam to the bodyor housing unit of the selector.

The upper route (1) takes on the shape of flat C, the extreme ends 12and 13 being of different length. Prolongation number 13 extends, fromits free transversal edge to a first section (14) which is bent at 180°to the prolongation (13), and to a second section bent outwards at anangle slightly more than 90°, which defines the lower route (11). Thisportion has a series of holes (15) to allow the passing of rivets oranchorage elements of the beam to the body of the selector.

The prolongation 12 and 13 run at a certain inclination, downwards fromthe control stretch.

The central stretch of the beam will have a sensor or measurer ofdeformations (16) attached to the lower part.

FIGS. 7 and 8 show the internal part of a coin selector in which thebeam (10), shown in FIGS. 5 and 6, is mounted.

FIGS. 7 reprents the stretch along which a coin (4), inserted into theselector, will follow. In front of the beam (10) is an anvil (18) onwhich the coin will fall which serves as a shock absorbing elementagainst the impact vibrations. In this case, the sensor 16 incorporatedin the beam (10), will detect only the deformations originating on thebeam as a result of the rolling or displacement of the coin along thebeam.

As can be seen from FIG. (8), the selector body has a lower stopper (19)and upper stopper (20) which limit the possibilities of oscilations ormovements of the beam (10).

The remaining components shown in FIGS. 7 and 8 correspond to those of atraditional selector.

In the case of FIG. (9), the upper stretch of the beam is referencemarked 10a and the lower stretch 11a. These two stretches are straightand converge on each other, remaining joined for an intermediate stretch(21) which is a prolongation and forms part of the tracts 10a and 11a,being perpendicular to the latter. Tract 10a will run along, as in thecase of FIGS. 1 to 6, at an inclination so as to facilitate the rollingof the coins 17. The sensor 16 is attached to the external surface ofthe intermediate stretch 21.

The beam unit illustrated in FIG. 7 adopts a general form C. None of theextreme ends of the tract (10a), which make up the rolling pathway, areincased. The incasement is defined by the C base or lower tract 11a.

Finally, FIG. 10 represents a configuration of the beam in the formapproximately of a T. The upper tract 10b and the lower tract 11b arestraight and converge as in the case of FIG. 7 and continue joined forthe length of the intermedoate tract 21b which forms part of the lowertract 11b and is independent from the upper tract 10b which determinesthe rolling pathway for coins (70). The intermediate tract 21b coincidesat an intermediate point on the upper tract 10b, to which it is joined.

In this case, none of the extremes of the ramp 10b are incased. As inthe case of FIG. 7, the lower tract 11a defines the incasement orattachment zones. The sensor 16 is attached to the external surface ofthe interemediate tract 21b. the signal obtained with this issymmetrical, with respect to the moment at which the coin passes overthe intermediate tract 21b.

FIG. 4 corresponds to a diagram of the electric signal which ensues fromthe deformations of the elastically deformable element, shown in FIG. 1,in the form of beam 2 incased at one end, during the impact and rollingof the coin (4). The electrical current obtained is also shown in thisdiagram, where the references t₀ and t₁ correspond to the moment ofcommencement and completion of the rolling of the coin on the beam whichmakes up the deformable elastic element.

The detailed analysis of the signal represented in FIG. 4 enables one toclearly distinguish two perfectly differentiated fields by thedissimilar activation of both. Firstly, the signals produced by thedeformation experienced in the beam, which constitutes the deformableelastic element, are detected at the moment of impact of the coin on thebeam, precisely up to the moment when the rolling is about to begin.These signals correspond to the graph in FIG. 4, to those observed nearthe moment t0, the moment of impact, immediately before the commencementof the rolling. Once the coin begins to roll along the beam, the signalscorresponding to the impact (instant t0) terminate and the vibrationswhich the coin beam unit produce begin to be activated by the rolling ofthe coin. The duration of these vibrations extends to the instant t1, inwhich the coin rolls along the sensored beam.

The invention uses the signals formely on, which in the graph of FIG. 4correspond to those observed around the instant t0. By means offrequency analysis techniques the frequencies corresponding to theresonance in relation to the type of impact are analyzed, hencedetermining a parameter which is representative of the mechanicalelasticity of the coin. For this purpose, as already indicated, theupper harmonics of the impact signal is measured, the content of thismeasurement being representative of the mechanical elasticity of thecoin.

These characteristics can be seen in the graph of FIGS. 11 and 12 in thefirst of which the frequency content of a legal tender coin is shown. Inthe graph of FIG. 12, the frequency content of a fake coin these graphis detected in the spectrum near the frequency, indicated by the pointF₁, corresponding to the moment of impact of the coin on the elasticallydeformable element.

As already indicated previously, a new parameter will be considered whencarrying out a measurement of the frequency contents present on impact,depending on the mechanical elasticity of the coin, for their storage inthe coin selector memory and their later help in identification,together with other parameters representative of the weight, alloy,dimensions, etc.

FIG. 13 corresponds to a block diagram of a circuit applicable to thefrequency analysis of the impact previously described.

In this circuit, reference mark 4 indicates a coin which will impact onthe elastically deformable element, to which the impact sensor 7, FIG. 1is related. The level of the signal delivered by sensor 7 is amplifiedby a block amplifier 22. Following, is an analogic pitch-band filtercircuit (23) the tuning of which is centered on the characteristicfrequency f₀ of the elasticity sought after.

After the filter is an analog/digital converter 24, which will send thedigital signal to a microprocessor (25) for processing, the filter (23)may be of fixed or variable pitch-band frequency, depending on whetherone or various ranges of frequency are involved.

The memory (26), in which the parameters corresponding to differentlegal tender coins will be stored and which will assist inidentification of the same, is connected to the microprosessor.

A digital filter can be used as an alternative to the analogic filter(23), incorporated in the microprocessor used in the coin selector.

When wishing to incorporate a measurement of the characteristicsvibrations present during the rolling of the coin along the beam, inother words the instances t₀ through t₁ of FIG. 4, a circuit similar tothat described in reference to FIG. 13 can be used, with the linkreference marked 27.

Reference 28 indicates the admission/rejection and control of signal.

We claim:
 1. An apparatus for detecting mechanical characteristics ofcoins in order to determine whether the coins are authentic, theapparatus comprising:an elastically deformable element capable of beingdeformed by the weight of a coin, the element being in the form of abeam having a fixed portion and an overhanging portion; said beamdefining a rolling path along which a coin can travel, the beam beingdeformable by the rolling coin to an extent which depends on the weightof the coin and the position of the coin relative to the fixed portionof the beam; and the beam having means for measuring deformation of thebeam as the coin travels therealong; wherein the measuring means is forproviding a signal based on the measured deformations that isrepresentative of the mechanical elasticity of the coin which can becompared with stored data to determine whether or not the coin isauthentic.
 2. An apparatus according to claim 1, wherein said beam ismade up of an elastic band which is fixed at one end while the other endis overhanging.
 3. An apparatus according to claim 1, wherein thedeformation measuring means consists of at least one extensometric gageattached to the beam near its fixed portion.
 4. An apparatus accordingto claim 1, wherein the deformation measuring means consists of at leastone displacement sensing device attached to the beam near its fixedportion.
 5. An apparatus according to claim 2, wherein the beam is fixedat its overhanging portion.
 6. An apparatus according to claim 1,wherein the beam is fixed at both ends.
 7. An apparatus according toclaim 1, wherein said beam comprises an upper tract, which defines therolling path for the coins, and a lower tract which defines an anchoringzone for the unit to the body or housing unit of the selector; with thefirst tract running at an inclination in order to provoke the rolling ofthe coins.
 8. An apparatus according to claim 7, wherein the upper tractadopts a configuration in the form of flat C, the arms of which are ofdifferent length, the longer prolongation extending to a first sectionwhich is bent at 180° under itself, and a second section bendingoutwards at an angle of slightly more than 90°, hence defining the loweranchorage tract, with the sensor being attached underneath the centralarm of the upper tract.
 9. An apparatus according to claim 7, whereinthe upper and lower tracts are straight and converging, remainingjoinend by their divergent extremes via an intermediate stretch which isa prolongation of both tracts, making up one single piece and isperpendicular to the lower anchorage tract, the sensor being attachedlaterally to the intermediate stretch.
 10. An apparatus according toclaim 7, wherein the upper and lower tracts are straight and convergeand remain joined for a straight intermediate stretch which is aprolongation of the lower tract with which it forms an angle of 90°,coming together and joining underneath at an intermediate point of theupper stretch the sensor being attached laterally to the intermediatestretch.
 11. An apparatus according to claim 1, wherein a shockabsorbing member is disposed adjacent said beam for receiving a droppedcoin and guiding the coin onto the beam.
 12. An apparatus fordetermining the mechanical characteristics of coins, the apparatuscomprising:an elastic element capable of being deformed by the weight ofa coin, the element being in the form of a beam having a fixed portion,said beam defining a rolling path along which a coin can travel andbeing deformable by the coin to an extent which depends on the weight ofthe coin and the position of the coin relative to the fixed portion ofthe beam; the beam including an upper tract and a lower tract, the uppertract defining said rolling path and the lower tract defining said fixedportion, said upper tract being disposed at an inclination to facilitaterolling of the coin; the upper tract being in the form of a flattened Cshape with two arms of different length and a central section, thelonger arm having a first section bent 180° under itself and a secondsection bent outwardly away from the central section at an angle ofabout 90° to form said lower tract; and the beam having means disposedon a side of the central section opposite said rolling path for sensingdeformation of the beam.
 13. An apparatus for determining the mechanicalcharacteristics of coins, the apparatus comprising:an elastic elementcapable of being deformed by the weight of a coin, the element being inthe form of a beam having a fixed portion, said beam defining a rollingpath along which a coin can travel and being deformable by the coin toan extent which depends on the weight of the coin and the position ofthe coin relative to the fixed portion of the beam; the beam includingan upper tract and a lower tract, the upper tract defining said rollingpath and the lower tract defining said fixed portion, said upper tractbeing disposed at an inclination to facilitate rolling of the coin; theupper tract and lower tract formed of a one-piece member with the lowertract extending substantially horizontal, an intermediate portionsubstantially perpendicular to and extending upward from the lowertract, and the upper tract extending from said intermediate portion atan inclination so as to converge with the lower tract; the beam havingmeans disposed on the intermediate portion for sensing deformation ofthe beam.
 14. An apparatus for determining the mechanicalcharacteristics of coins, the apparatus comprising:an elastic elementcapable of being deformed by the weight of a coin, the element being inthe form of a beam having a fixed portion, said beam defining a rollingpath along which a coin can travel and being deformable by the coin toan extent which depends on the weight of the coin and the position ofthe coin relative to the fixed portion of the beam; the beam includingan upper tract and a lower tract, the upper tract defining said rollingpath and the lower tract defining said fixed portion, said upper tractbeing disposed at an inclination to facilitate rolling of the coin; theupper tract and lower tract converging and being connected by anintermediate portion that extends between the two tracts, theintermediate portion forming an extension of the lower tract that issubstantially perpendicular thereto, said intermediate portion beingjoined to the upper tract at substantially the midpoint thereof; and thebeam having means disposed on the intermediate portion for sensingdeformation of the beam.